Water has a huge economic, social and environmental importance, so the search of the precious liquid has become an intensive process in water policies of different countries. Therefore, the provision of water suitable for human consumption has now become a problem of vital importance for the population. The water desalination has led to a new strategy for water supply, especially in areas with high water stress and with opportunities of abundant new alternative sources of supply (seawater and brackish). Desalination technologies allow greater savings and efficiency in water use, exploitation of resources that were unusable previously like the peculiar case of sea water, as well as a greater guarantee of supply in terms of availability and quality, particularly in areas with poor water resources. In these areas often merge several factors that greatly favor the use of desalination. The Canary Islands are a clear example of this, as it has a large population, a great tourist industry, a shortage of the liquid element and a high demand for agricultural irrigation that conditions the availability and the need of new sources of high quality water. Water desalination, in the water policy of the Canary Islands, has been deeply rooted in the last forty years, allowing to solve and overcome the shortage and to ensure a quality suitable for human consumption. This article discusses the importance and significance that has had water desalination in the Canary Islands, made with a historical development of the evidence and key outcomes.